The present invention relates to a control system for performing remote control functions on a rotating object from a stationary location or object. In the application of the preferred embodiment of the invention as disclosed in this patent application, the control system comprises a single channel, four function-select, power transmission system with an encoder at the stationary location and a decoder on the rotating object.
Many types of rotating devices such as rotary clamps, indexing chucks, or spindle mounted balancers, sometimes require independent control of several mechanisms on the rotating portion of the device. Where control is performed electrically, slip rings are usually employed to conduct control signals between stationary and rotary elements. One ring is used per control function plus a ring for the common line. Thus if four different functions are to be controlled on a rotating object, a total of five slip rings would be used.
Under operating conditions of high speed, high current, and a contaminating environment, slip rings have shown limited service life. One way to improve reliability of slip rings is to reduce ring diameter, which results in lower surface speed between brush and ring. This concept can be carried further by reducing the diameter of rubbing surfaces to a mere center point wherein the ring and brush as such are eliminated. A conical cup replaces the ring and a conical point riding in the cup acts as the brush. Of course only one point/cup assembly hereinafter sometimes referred to as "center contact" can be used on one end of the shaft in order to complete a circuit. A second center contact must be used on the opposite end of the shaft.
While the center contact design solves problems attendant to slip rings, it provides only a single channel. In order to control more than one function on a rotating body, a signal transmitted through this signal channel must be modified in some way to represent a code containing function-select information. So called single channel data transmissions, as found in communication and computer art, utilize multiplexing techniques to transmit numerous messages simultaneously. Other approaches include amplitude or frequency modulation, or variable phase shifting of two superimposed signals.
Applicant has invented new control systems as illustrated in his prior allowed U.S. patent applications, Ser. Nos. 342,450 and 358,999.
Where significant power must also be delivered over a single channel along with signal information, the size and cost of the required hardware to develop an appropriate system for delivering both power and function-select information can be expensive.
In one respect the present invention is directed to a new and improved control system for the remote control of multiple functions on a rotating object which affords a significant cost saving over such more expensive systems.
The present invention permits transmission of relatively high electrical power levels over two wires via a waveform encoded to select particular functions to be performed. Thus a center contact at each end of a spindle, or shaft, supporting a rotating object enables both power transmission and function-select control capabilities to be provided for a rotating body without the use of slip rings.
In the preferred embodiment disclosed herein, the encoded waveform makes it possible to select up to four control functions.
The present invention arises in part through the recognition that a sinusoidal waveform is readily susceptible to two basic transformations. One, a full wave to half wave transformation by means of a diode, and two, a polarity reversal using a double-pole, double-throw relay, by way of example. Four combinations are then available: (1) a positive full wave (+FW); (2) a negative full wave (-FW); (3) a positive half wave (+HW); (4) a negative half wave (-HW).
One of these four combinations is transmitted via the center contacts to the rotating object and the rotating object contains a receiving circuit which decodes the signal and which causes power from the signal to be applied to the appropriate function which is to be controlled.
The control system comprises transmitting circuitry on the stationary portion and the coupling means between the transmitting circuit and the receiving circuit. The coupling means includes the center contacts at opposite ends of the spindle on which the rotating object is supported for rotation. Thus, in addition to avoiding the use of slip rings, the invention simplifies upon the circuitry for both transmitting circuit and receiving circuit whereby a more economical construction results.
Because the power waveform which is transmitted from the stationary object to the rotating object is itself inherently representative of the particular coding information, there are essentially no signal-to-noise problems which need to be addressed in use of the present invention. This is in contrast to other controls where a coded signal is superimposed on a power waveform.
While the present invention has application to a variety of different types of rotating devices, such as those mentioned above, the present invention is disclosed herein as applied to a spindle mounted balancer employing principles of applicant's prior allowed patent applications as referred to above.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.